This research project involves the use of classical conditioning and electrodermal response habituation and dishabituation paradigms to investigate the basic learning processes of normal and retarded children. The research utilizes trace and delay conditioning situations, with masking stimuli used to terminate the information processing of stimuli, in order to obtain information concerning the input, registration, and processing of auditory and visual information. The long term objective of the program is to understand better the learning and information processing characteristics of normal, retarded, and high risk children and to provide procedures to aid in distinguishing between the moderately and mildly retarded child who performs at a subaverage level due to motivation or cultural factors, and the retarded child who is retarded due to limitations imposed by functional or structural characteristics of the nervous system.